1. Field of the Invention
The present invention relates to a thin-film magnetic head device having a magnetic structure of such a type that a magnetic gap layer is interposed between upper and lower magnetic layers at a surface of the device facing a recording medium.
2. Description of the Related Art
There have recently been made approaches for subjecting a magnetic head device employed in a magnetic disc apparatus to a high density to meet the performance of a recording medium such as a magnetic disc and for activating the magnetic head device with high efficiency. The magnetic head device has progressively been rendered small in size and greatly improved in view of its accuracy. In order to meet the demand referred to above, there have been proposed various kinds of small thin-film magnetic head devices of a type wherein high-density magnetic recording can be carried out in a state in which a magnetic field distribution of the leading end of a magnetic pole contributing to magnetic recording is sharp. These thin-film magnetic head devices have already been put to practical use.
FIG. 5 shows one example of an arrangement of one of such thin-film magnetic head devices. A thin-film magnetic head device A shown in FIG. 5 is structurally formed in the following manner. Described specifically, a lower magnetic layer 14 and a gap layer 10 are formed on a substrate 24 through a lower insulating layer 26. There is also formed on a combination of the lower magnetic layer 14 and the gap layer 10, conductive coils 22 enveloped by an interlayer insulating layer 20. In addition, an upper magnetic layer 12 and a covering layer 16 are formed on a combination of the lower magnetic layer 14, the gap layer 10 and the conductive coils 22. Now, each of the upper and lower magnetic layers 12, 14 is normally made of a permalloy.
The thin-film magnetic head device A having this type of structure suffers one serious disadvantage under the present conditions. Described specifically, the use of the upper and lower magnetic layers 12, 14 each made of the permalloy makes the device A inferior in its recording characteristic as compared with other types of magnetic head devices except for a thin-film magnetic head device using a magnetic member having a magnetic characteristic superior to that of the permalloy. The process of writing magnetic information into a magnetic recording medium having a high coercive force is rendered difficult in particular. Thus, if each of the upper and lower magnetic layers 12, 14 is formed of a magnetic material having a magnetic characteristic superior to that of the permalloy which has widely been used, then the recording characteristic can be improved. This has been definitely shown by various simulations and experiments.
When the upper and lower magnetic layers 12, 14 are composed of known thin films (e.g., a thin film of an amorphous alloy, a thin film of an Fe-N alloy, etc.) each having a high magnetic flux density and a high magnetic permeability, these films are, however, unstable to heat and nonresistant to corrosion, thereby causing the problem that they are impractical in use. On the other hand, when a magnetic material stable to heat, which has adjusted its components and its manufacturing conditions, are used to produce a magnetic material having a high magnetic flux density, the magnetic permeability of such a magnetic material cannot be rendered high.